MySQL CASE to update multiple columns

I would like to update multiple columns in my table using a case statement, but I cannot find how to do this (is this even possible). I came up with the following invalid reference query:

UPDATE …

Meaning of (+) in SQL queries

I’ve come across some SQL queries in Oracle that contain ‘(+)’ and I have no idea what that means. Can someone explain its purpose or provide some examples of its use?
Thanks

How does GROUP BY work?

Suppose I have a table Tab1 with attributes – a1, a2, … etc. None of the attributes are unique.

What will be the nature of the following query? Will it return a single row always?

SELECT a1, a2, …